JP2018051980A - Injection hole plate, liquid injection head, and liquid injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection hole plate which can change a drop size according to its purpose and achieves excellent merchantability, and to provide a liquid injection head and a liquid injection device.SOLUTION: The invention relates to a nozzle plate 51 formed with a small diameter nozzle hole 81 and a large diameter nozzle hole 82 which is formed so as to have a diameter larger than the small diameter nozzle hole 81 and communicates with the small diameter nozzle hole 81 at the downstream side of the small diameter nozzle hole 81 in an ink flow direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an ejection hole plate, a liquid ejection head, and a liquid ejection apparatus.

  2. Description of the Related Art As an apparatus that discharges ink droplets onto a recording medium (for example, recording paper) and records information (for example, images and characters) on the recording medium, there is an ink jet printer including an ink jet head. The inkjet head has an actuator plate in which a channel filled with ink is formed, and a nozzle plate having a nozzle hole communicating with the channel. In the ink jet head, the actuator plate is deformed so that the volume in the channel expands and contracts, so that the ink filled in the channel is ejected through the nozzle holes.

Here, for example, Patent Document 1 below discloses a configuration in which a large-diameter nozzle hole and a small-diameter nozzle hole having a smaller diameter than the large-diameter nozzle hole are formed in the nozzle plate. The large-diameter nozzle holes and the small-diameter nozzle holes are formed alternately in the nozzle plate, for example, in the channel arrangement direction. The large diameter nozzle hole and the small diameter nozzle hole communicate with different channels.
According to this configuration, by ejecting ink from each of the large diameter nozzle hole and the small diameter nozzle hole, large droplet ink is ejected through the large diameter nozzle hole, and small droplet ink is ejected through the small diameter nozzle hole. Discharged. Thereby, it is said that ink of the same color and different droplet sizes can be ejected, and information rich in gradation can be recorded.

JP 2006-272614 A

  Recently, a configuration in which the droplet size of ink ejected from an inkjet head is changed according to the purpose (for example, high-speed printing or high-resolution printing) has been studied. As such a configuration, a configuration in which a small droplet mode in which ink is ejected from a small diameter nozzle hole and a large droplet mode in which ink is ejected from a large diameter nozzle hole can be considered.

  However, in the configuration of Patent Document 1 described above, since the large-diameter nozzle holes and the small-diameter nozzle holes are alternately formed, the adjacent nozzle holes with the same diameter are compared to the case where only the nozzle holes with the same diameter are arranged. The arrangement pitch between them becomes wider. For this reason, there is a limit to narrowing the pitch of droplets during printing, and it is difficult to improve resolution.

  Further, the surface tension (meniscus strength) acting on the inner surface of each nozzle hole varies depending on the inner diameter of the nozzle hole. Therefore, when a plurality of nozzle holes having different inner diameters are opened on the same plane of the nozzle plate, it is difficult to form an appropriate meniscus at each nozzle hole. Further, in order to form an appropriate meniscus with each nozzle hole opening on the same plane of the nozzle plate, there is a limit to increasing the inner diameter difference between the small diameter nozzle hole and the large diameter nozzle hole. As a result, it is difficult to increase the difference in droplet size between the small droplet mode and the large droplet mode.

  The present invention has been made in view of such circumstances, and provides an ejection hole plate, a liquid ejecting head, and a liquid ejecting apparatus that can change the droplet size according to the purpose and are excellent in merchantability. That is.

  In order to solve the above problems, an injection hole plate according to an aspect of the present invention has a plate body in which a first injection hole and a second injection hole for injecting a liquid are formed, and the second injection hole includes: The first injection hole is formed with a larger diameter and communicates with the first injection hole on the downstream side in the liquid flow direction with respect to the first injection hole.

  According to this configuration, for example, the size of the droplet ejected from the liquid ejecting head can be changed by changing the pressure of the liquid in the channel communicating on the upstream side of the ejecting hole. That is, in this aspect, a small droplet mode in which a small droplet is ejected in a state where a meniscus is formed in a first ejection hole, and a large droplet mode in which a large droplet is ejected in a state where a meniscus is formed in a second ejection hole. And can be switched to. In this case, in the small droplet mode, the printing range with one droplet can be made smaller than in the large droplet mode. Accordingly, for example, by increasing the driving frequency as compared with the large droplet mode, the pitch of the droplets in the scanning direction of the liquid ejecting head can be narrowed, and high-resolution printing can be realized. On the other hand, in the large droplet mode, the printing range with one droplet can be increased as compared with the small droplet mode, so that high-speed printing can be realized. As described above, since the small droplet mode and the large droplet mode can be switched according to the pressure in the channel, for example, the droplet size of the liquid ejected from the liquid ejecting head can be easily changed according to the purpose. can do.

In particular, in this aspect, since the first injection holes and the second injection holes are formed to communicate with each other in the liquid flow direction, for example, the first injection holes and the second injection holes are alternately arranged on the same plane of the plate body. Compared with the case where it opens, the arrangement pitch of adjacent injection holes of the same diameter can be narrowed. Thereby, the pitch of the droplets in the arrangement direction of the injection holes can be narrowed, and the resolution can be improved.
Moreover, since the injection hole plate of this aspect has the same diameter injection hole opened on the same plane of the plate body, compared to the case where a plurality of injection holes with different inner diameters are opened on the same plane, An optimum meniscus can be easily formed for each injection hole. In addition, since an optimum meniscus can be easily formed in each injection hole, a difference in inner diameter between the first injection hole and the second injection hole can be secured, and the droplet size between the small droplet mode and the large droplet mode can be secured. It is also possible to increase the difference.

In the above aspect, the connection surface connecting the downstream end edge in the flow direction in the first injection hole and the upstream end edge in the flow direction in the second injection hole in the plate body is hydrophilic. You may have.
According to the above aspect, for example, when switching from the small droplet mode to the large droplet mode, the liquid overflowing from the first injection hole can be wetted and spread on the connection surface. Thereby, it is possible to suppress the ink overflowing from the first ejection holes from dripping directly from the first ejection holes through the second ejection holes (without being wetted and spread on the connection surfaces and the inner surfaces of the second ejection holes). As a result, the second injection hole can be filled with liquid in the large droplet mode.

The said aspect WHEREIN: The opening surface which the downstream opening of the said distribution direction in the said 2nd injection hole opens among the said plate main bodies may have water repellency.
According to the above aspect, since it is possible to suppress the liquid from spreading on the opening surface, it is possible to suppress the liquid from leaking from the second injection hole when switching from the small droplet mode to the large droplet mode, for example.

In the above aspect, the plate body is laminated on the downstream side in the flow direction with respect to the first plate in which the first injection hole is formed, and the second injection hole is formed in the first plate. And two plates.
According to the said aspect, after forming a 1st injection hole and a 2nd injection hole in each plate, respectively, an injection hole plate can be formed by laminating | stacking each plate. Therefore, the injection hole plate can be easily manufactured as compared with the case where the first injection hole and the second injection hole that are continuous in the flow direction are formed on one plate.

In the above aspect, the plate body has an intermediate plate disposed between the first plate and the second plate, and the intermediate plate includes a downstream opening in the flow direction in the first injection hole. A communication hole that communicates with the upstream opening of the second injection hole in the flow direction may be formed, and an inner diameter of the communication hole may be greater than or equal to an inner diameter of the second injection hole.
According to the above aspect, the liquid meniscus formed by the interaction (surface tension or the like) with the inner surface of the second injection hole can be accommodated in the second injection hole (and in the communication hole). That is, since the liquid level of the meniscus can be arranged in the second injection hole (and in the communication hole), the meniscus formed in the second injection hole cannot be accommodated in the second injection hole, and the meniscus is destroyed. Can be suppressed. Therefore, an appropriate meniscus can be stably formed in the second injection hole.
Further, since the communication hole communicates the downstream opening of the first injection hole and the upstream opening of the second injection hole, the communication hole is also filled with the liquid in the large droplet mode. In this case, since the inner diameter of the communication hole is formed to be equal to or larger than the inner diameter of the second injection hole, the liquid directly flows into the second injection hole from the first injection hole having a smaller diameter than the second injection hole. The liquid can be smoothly circulated in the second injection hole. That is, since the communication hole functions as a buffer for holding liquid between the first injection hole and the second injection hole, it is possible to suppress the occurrence of insufficient supply of liquid into the second injection hole in the large droplet mode. it can.

The said aspect WHEREIN: The length of the said flow direction in the said 2nd injection hole may be longer than the length of the said flow direction in the said 1st injection hole.
According to the above aspect, the liquid meniscus formed by the interaction (surface tension or the like) with the inner surface of the second injection hole can be accommodated in the second injection hole. That is, since the liquid level of the meniscus can be disposed in the second injection hole, it is possible to prevent the meniscus from being destroyed without being able to be accommodated in the second injection hole. Therefore, an appropriate meniscus can be stably formed in the second injection hole.

A liquid ejecting head according to an aspect of the present invention is disposed on the upstream side in the flow direction with respect to the ejection hole plate of the above aspect and the ejection hole plate, and communicates with the second ejection hole through the first ejection hole. And an actuator plate having a channel.
According to the said aspect, since the ejection hole plate of the said aspect is provided, the liquid ejecting head excellent in commercial property can be provided.

A liquid ejecting apparatus according to one embodiment of the present invention includes the liquid ejecting head according to the above aspect.
According to the above aspect, since the liquid ejecting head according to the above aspect is provided, it is possible to provide a liquid ejecting apparatus having excellent merchantability.

  According to one embodiment of the present invention, it is possible to provide an ejection hole plate, a liquid ejecting head, and a liquid ejecting apparatus that can change the droplet size according to the purpose and have excellent merchantability.

1 is a schematic configuration diagram of an inkjet printer according to an embodiment. It is a schematic block diagram of the inkjet head, main tank, sub tank, and ink circulation mechanism which concern on 1st Embodiment. 1 is a schematic cross-sectional view of an inkjet head according to a first embodiment. It is sectional drawing which follows the IV-IV line of FIG. It is the bottom view which looked at the nozzle plate in 1st Embodiment from the downward direction. It is a schematic block diagram corresponding to FIG. 3 for demonstrating small droplet mode. It is a schematic block diagram corresponding to FIG. 3 for demonstrating a large droplet mode. It is sectional drawing corresponding to FIG. 4 of the inkjet head which concerns on 2nd Embodiment.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the following embodiments, an ink jet printer (hereinafter simply referred to as a printer) that performs recording on a recording medium using ink (liquid) will be described as an example. In the drawings used for the following description, the scale of each member is appropriately changed in order to make each member a recognizable size.

(First embodiment)
[Printer]
FIG. 1 is a schematic configuration diagram of the printer 1.
As shown in FIG. 1, the printer 1 according to the present embodiment includes a pair of transport mechanisms 2 and 3, a scanning mechanism 4, an inkjet head 5, a main tank 6, sub tanks 8 and 9, an ink circulation mechanism 10, and the like in a housing 15. It is mounted and configured.

  In the following description, an X, Y, Z orthogonal coordinate system is used as necessary. In this case, the X direction coincides with the transport direction of the recording medium P (for example, paper). The Y direction coincides with the scanning direction of the scanning mechanism 4. The Z direction is a direction orthogonal to the X direction and the Y direction. The printer 1 according to the present embodiment is mounted and used so that the X direction and the Y direction are horizontal directions and the Z direction is a gravity direction.

  The transport mechanisms 2 and 3 transport the recording medium P in the X direction. Specifically, the transport mechanism 2 includes a grit roller 11 extending in the Y direction, a pinch roller 12 extending in parallel to the grit roller 11, and a drive mechanism such as a motor that rotates the grit roller 11 (not configured). (Shown). The transport mechanism 3 includes a grit roller 13 that extends in the Y direction, a pinch roller 14 that extends in parallel to the grit roller 13, and a drive mechanism (not shown) that rotates the grit roller 13. Yes.

  The scanning mechanism 4 reciprocates the inkjet head 5 in the Y direction. Specifically, the scanning mechanism 4 includes a pair of guide rails 21 and 22 that extend in the Y direction, a carriage 23 that is movably supported by the pair of guide rails 21 and 22, and moves the carriage 23 in the Y direction. And a drive mechanism 24 to be operated.

  The drive mechanism 24 is disposed between the guide rails 21 and 22 in the X direction. The drive mechanism 24 is a pair of pulleys 25 and 26 disposed at intervals in the Y direction, an endless belt 27 wound between the pair of pulleys 25 and 26, and a drive that rotationally drives one pulley 25. And a motor 28.

The carriage 23 is connected to an endless belt 27. A plurality of inkjet heads 5 are mounted on the carriage 23 in a state of being arranged in the Y direction.
Each inkjet head 5 is configured to be able to eject inks of different colors such as yellow, magenta, cyan, and black.

  The main tank 6 is provided in the casing 15 separately from the ink jet head 5 (carriage 23). A plurality of main tanks 6 are provided in the housing 15 in the X direction. In each main tank 6, different color inks are accommodated corresponding to the above-described ink jet heads 5.

  The sub tanks 8 and 9 are mounted on the carriage 23 together with the ink jet head 5. The sub tanks 8 and 9 are a supply sub tank 8 that supplies ink to the inkjet head 5 and a discharge sub tank 9 that stores ink discharged from the inkjet head 5. These supply sub-tank 8 and discharge sub-tank 9 are provided in each inkjet head 5. Accordingly, each supply sub-tank 8 and discharge sub-tank 9 contains ink of a color corresponding to each color inkjet head 5.

FIG. 2 is a schematic configuration diagram of the inkjet head 5, the main tank 6, the sub tanks 8 and 9, and the ink circulation mechanism 10. The ink jet head 5, the main tank 6, the sub tanks 8 and 9, and the ink circulation mechanism 10 have the same configuration except for the color of the supplied ink. Therefore, in the following description, one ink jet head 5, the main tank 6, the sub tanks 8 and 9, and the ink circulation mechanism 10 will be described as an example.
As shown in FIG. 2, the ink circulation mechanism 10 includes a circulation flow path 34 having an ink supply pipe 31, an ink discharge pipe 32, and an ink recovery pipe 33, a supply pump 35, a suction pump 36, a recovery pump 37, have.

The ink supply pipe 31 connects between the main tank 6 and the supply pump 35, between the supply pump 35 and the supply subtank 8, and between the supply subtank 8 and the inkjet head 5.
The ink discharge pipe 32 connects between the inkjet head 5 and the suction pump 36 and between the suction pump 36 and the discharge sub-tank 9.
The ink recovery pipe 33 connects between the discharge sub-tank 9 and the recovery pump 37 and between the recovery pump 37 and the main tank 6.

The supply pump 35 sends the ink in the main tank 6 to the supply sub tank 8 through the ink supply pipe 31.
The suction pump 36 sends the ink in the inkjet head 5 to the discharge sub-tank 9 through the ink discharge pipe 32.
The recovery pump 37 sends the ink in the discharge sub-tank 9 through the ink recovery pipe 33 to the main tank 6. In the present embodiment, so-called tube pumps are used for the pumps 35 to 37.

<Inkjet head>
FIG. 3 is a schematic cross-sectional view of the inkjet head 5. 4 is a cross-sectional view taken along line IV-IV in FIG.
As shown in FIGS. 3 and 4, the inkjet head 5 is a so-called circulation side chute type in which ink is ejected from a central portion in the Y direction in a later-described ejection channel 62. Specifically, the inkjet head 5 includes a nozzle plate 51, an actuator plate 52, a cover plate 53, and a flow path plate 54. The nozzle plate 51, the actuator plate 52, the cover plate 53, and the flow path plate 54 are configured to be stacked in this order in the Z direction. In the following description, in the inkjet head 5, the nozzle plate 51 side in the Z direction is set as the lower side, and the flow path plate 54 side in the Z direction is set as the upper side.

  The inkjet head 5 is mounted on the carriage 23 (see FIG. 1) so that the nozzle plate 51 faces downward. Thereby, each inkjet head 5 is comprised so that a droplet can be discharged toward the downward direction.

  The actuator plate 52 is made of a piezoelectric material such as PZT (lead zirconate titanate). For the actuator plate 52, a so-called monopole type substrate in which the polarization direction is set in one direction along the Z direction is used. The actuator plate 52 may be a so-called chevron type substrate formed by laminating two piezoelectric substrates having different polarization directions in the Z direction.

  A channel row 61 is formed in the actuator plate 52. The channel row 61 includes an ejection channel 62 that is filled with ink and a non-ejection channel 63 that is not filled with ink (see FIG. 4). The channel row 61 is configured by alternately arranging discharge channels 62 and non-discharge channels 63 with an interval in the X direction.

  Each of the channels 62 and 63 extends with the Y direction as a longitudinal direction, and at least a part thereof penetrates the actuator plate 52 in the Z direction. Drive electrodes (not shown) are formed on the inner surfaces of the channels 62 and 63. In the present embodiment, a configuration in which the channel row 61 is one row will be described, but the configuration is not limited to this. That is, two channel rows 61 may be formed at intervals in the Y direction. In this case, it is preferable that the ejection channels 62 and the non-ejection channels 63 of each channel row 61 are arranged in a staggered manner. However, the pitch of the channels 62 and 63 can be changed as appropriate. The channel column 61 may be a plurality of columns of three or more.

As shown in FIG. 3, the cover plate 53 is joined to the upper surface of the actuator plate 52 so as to close the channels 62 and 63. The cover plate 53 is formed with an inlet opening 65 and an outlet opening 66 that communicate with the discharge channel 62 described above. Each opening penetrates the cover plate 53 in the Z direction.
The inlet opening 65 communicates with the first end portion in the Y direction in the discharge channel 62. The outlet opening 66 communicates with the second end portion in the Y direction in the discharge channel 62. The openings 65 and 66 may be formed for the discharge channels 62, respectively. The openings 65 and 66 may be formed so as to communicate with the discharge channels 62 collectively.

  The flow path plate 54 is joined to the upper surface of the cover plate 53 so as to close the openings 65 and 66. A supply channel 68 and a discharge channel 69 are formed in the channel plate 54. The supply flow path 68 communicates with the discharge channel 62 through the inlet opening 65 described above. The downstream end of the ink supply pipe 31 (see FIG. 2) is connected to the supply flow path 68. The discharge channel 69 communicates with the discharge channel 62 through the outlet opening 66 described above. Further, the upstream end portion of the ink discharge pipe 32 described above is connected to the discharge flow path 69.

FIG. 5 is a bottom view of the nozzle plate 51 as viewed from below.
As shown in FIGS. 4 and 5, the nozzle plate 51 is joined to the lower surface of the actuator plate 52 so as to close the channels 62 and 63 from below. The nozzle plate 51 has a nozzle hole 71 penetrating the nozzle plate 51 in the Z direction. A plurality of nozzle holes 71 are formed at the same pitch as the discharge channel 62 and spaced in the X direction. Each nozzle hole 71 communicates with each discharge channel 62 individually. As shown in FIG. 3, the nozzle hole 71 is formed in the nozzle plate 51 so as to be positioned at the center of the corresponding discharge channel 62 in the Y direction.

  Here, the nozzle plate (injection hole plate, plate body) 51 of the present embodiment is configured by stacking two plates 76 and 77 in the Z direction. Specifically, the nozzle plate 51 includes a first plate 76 and a second plate 77 joined to the lower surface of the first plate 76. Each plate 76 is made of a hydrophilic material (for example, polyimide). The plates 76 and 77 may be formed of a metal material (SUS or the like), glass, or the like. Further, the plates 76 and 77 may have a laminated structure of different materials.

  The nozzle hole 71 described above passes through the plates 76 and 77 in the Z direction. The nozzle hole 71 includes a small-diameter nozzle hole 81 and a large-diameter nozzle hole 82 that are continuous in the Z direction (ink distribution direction). Specifically, the small diameter nozzle hole 81 penetrates the first plate 76 in the Z direction. The small diameter nozzle hole 81 is formed in a tapered shape whose inner diameter gradually decreases as it goes downward. In the present embodiment, the inner diameter φ1 of the lower end opening of the small diameter nozzle hole 81 is, for example, about 10 μm to 30 μm.

  The large-diameter nozzle hole 82 penetrates the second plate 77 in the Z direction. The large diameter nozzle hole 82 communicates with the small diameter nozzle hole 81 through the upper end opening. In the present embodiment, the large diameter nozzle hole 82 is disposed coaxially with the small diameter nozzle hole 81. The large-diameter nozzle hole 82 is formed in a tapered shape whose inner diameter gradually decreases as it goes downward. The center of the large diameter nozzle hole 82 may be slightly shifted from the center of the small diameter nozzle hole 81 in the X direction and the Y direction.

  In the present embodiment, the inner diameter φ2 of the lower end opening of the large diameter nozzle hole 82 is, for example, about 25 μm to 50 μm. The dimensions of the nozzle holes 81 and 82 are appropriately changed as long as the meniscus can be formed in the nozzle holes 81 and 82 due to the interaction (surface tension, etc.) with the inner surfaces of the nozzle holes 81 and 82. Is possible. For example, the inner diameter of the upper end opening in the large-diameter nozzle hole 82 may be larger than the width of the discharge channel 62 in the X direction.

  In the present embodiment, the thickness of the second plate 77 (the length of the large diameter nozzle hole 82 in the Z direction) is larger than the thickness of the first plate 76 (the length of the small diameter nozzle hole 81 in the Z direction). It is thick. In this case, the thickness (for example, about 50 μm) of the second plate 77 is not less than the radius of the lower end opening in the large diameter nozzle hole 82 (that is, not less than the maximum depression amount in the Z direction of the meniscus formed in the large diameter nozzle hole 82). ) Is preferably set. In the present embodiment, the above-mentioned “dent amount” is a distance in the Z direction between the uppermost position of the liquid surface of the meniscus and the lower end opening edge of the large-diameter nozzle hole 82. However, the thickness of each plate 76 and 77 can be changed as appropriate.

  In the present embodiment, the lower surface of the second plate 77 is subjected to water repellent (liquid repellent) treatment. As described above, the plates 76 and 77 are made of a hydrophilic material. Therefore, a portion other than the lower surface of the second plate 77 (for example, a portion of the lower surface of the first plate 76 exposed in the large diameter nozzle hole 82 (the upper end edge of the large diameter nozzle hole 82 and the lower end edge of the small diameter nozzle hole 81) The connection surface 76a) and the inner surfaces of the nozzle holes 81 and 82 are maintained hydrophilic.

  The nozzle plate 51 of the present embodiment can be manufactured by joining the first plate 76 in which the small diameter nozzle hole 81 is formed and the second plate 77 in which the large diameter nozzle hole 82 is formed. . In this case, the nozzle holes 81 and 82 can be formed by, for example, laser processing or etching processing.

[How the printer works]
Next, a method for recording information on the recording medium P using the printer 1 described above will be described. In the following description, it is assumed that, as an initial state, the main tank 6 and the sub tanks 8 and 9 shown in FIG. Further, it is assumed that the ink jet head 5 is also filled with ink.

  In such an initial state, when the printer 1 shown in FIG. 1 is operated, the grit rollers 11 and 13 of the transport mechanisms 2 and 3 are rotated, so that the grit rollers 11 and 13 and the pinch rollers 12 and 14 are separated. The recording medium P is conveyed in the X direction. At the same time, the drive motor 28 rotates the pulley 25 to cause the endless belt 27 to travel. As a result, the carriage 23 reciprocates in the Y direction while being guided by the guide rails 21 and 22.

<Operation method of inkjet head>
Next, the operation of the inkjet head 5 will be described in detail below.
In the circulation side chute type inkjet head 5 as in the present embodiment, the supply pump 35, the suction pump 36 and the recovery pump 37 are operated to circulate ink in the circulation flow path 34. Specifically, the ink stored in the main tank 6 is supplied to the supply sub tank 8 through the ink supply pipe 31. Thereafter, the ink supplied into the supply sub tank 8 is supplied to the inkjet head 5 through the ink supply pipe 31. Ink supply from the supply sub tank 8 to the inkjet head 5 is performed by a water head difference between the supply sub tank 8 and the discharge sub tank 9.

  As shown in FIG. 3, the ink supplied to the inkjet head 5 is supplied into the ejection channel 62 through the supply flow path 68 and the inlet opening 65. Then, the ink passes through the discharge channel 62 and flows into the ink discharge pipe 32 (see FIG. 2) through the outlet opening 66 and the discharge flow path 69. The ink that has flowed into the ink discharge pipe 32 is then discharged to the discharge sub-tank 9. The ink is discharged from the inkjet head 5 to the discharge sub-tank 9 by the head difference between the supply sub-tank 8 and the discharge sub-tank 9 and the operation of the suction pump 36.

  When the ink discharged to the discharge sub-tank 9 exceeds a predetermined amount, it is sucked by the recovery pump 37. The ink sucked by the recovery pump 37 is returned to the main tank 6 through the ink recovery pipe 33. Thereby, ink circulates between the inkjet head 5 and the main tank 6.

  In the ink jet head 5, ink circulates between the ink jet head 5 and the main tank 6, and the ink is ejected toward the recording medium P in the process of reciprocating scanning of the carriage 23. That is, when a driving voltage is applied to the driving electrodes of the channels 62 and 63, the actuator plate 52 undergoes thickness sliding deformation, so that the discharge channel 62 expands and contracts. By this operation, the pressure in the ejection channel 62 increases and the ink is pressurized. As a result, the liquid droplets are discharged to the outside through the nozzle holes 71. Various information can be recorded on the recording medium P by the ejected ink landing on the recording medium P.

<How to change the droplet size>
Here, in the inkjet head 5 of this embodiment, the droplet size of the ink ejected from the inkjet head 5 can be changed by changing the pressure in the ejection channel 62. The inkjet head 5 of the present embodiment has a small droplet mode for discharging small droplets and a large droplet mode for discharging large droplets larger than the small droplet mode. In the following description, the small droplet mode is already set. Further, switching between the small droplet mode and the large droplet mode is performed at the home position of the carriage 23 (a position outside the upper area (printing area) of the recording medium P) or the like.

FIG. 6 is a schematic configuration diagram corresponding to FIG. 3 for explaining the small droplet mode.
As shown in FIG. 6, in the small droplet mode, an appropriate meniscus (hereinafter referred to as a small-diameter meniscus) is formed in the small-diameter nozzle hole 81 due to surface tension acting on the inner surface of the small-diameter nozzle hole 81. That is, in the small droplet mode, the pressure in the discharge channel 62 is maintained at an appropriate negative pressure (hereinafter referred to as a small diameter pressure) due to, for example, a water head difference between the supply sub-tank 8 and the discharge sub-tank 9. In this state, the inside of the discharge channel 62 is expanded and contracted by the operation method of the inkjet head 5 described above, whereby the ink is detached from the small-diameter meniscus. As a result, a small droplet having a size corresponding to the small-diameter meniscus falls downward. The small droplets detached from the small-diameter meniscus pass through the large-diameter nozzle hole 82 and are discharged to the outside from the nozzle hole 71. In the small droplet mode, a drive voltage having an appropriate frequency is applied to the drive electrode so that an appropriate small-diameter meniscus is formed in the small-diameter nozzle hole 81 before and after the discharge of the small droplet.

FIG. 7 is a schematic configuration diagram corresponding to FIG. 3 for explaining the large droplet mode.
As shown in FIG. 7, in the large droplet mode, an appropriate meniscus (hereinafter referred to as a large diameter meniscus) is formed in the large diameter nozzle hole 82. To switch from the small droplet mode to the large droplet mode, the pressure in the discharge channel 62 is increased from the small diameter pressure in the small droplet mode to the large diameter pressure in the large droplet mode. For example, the following method can be used to increase the pressure in the discharge channel 62. That is, the suction pump 36 provided in the ink discharge pipe 32 is stopped, and the ink circulation in the ink discharge pipe 32 is blocked. At this time, even if the ink flow through the ink discharge pipe 32 is interrupted, the ink is continuously supplied to the inkjet head 5 due to the water head difference between the supply sub-tank 8 and the discharge sub-tank 9. Thereby, the inside of the discharge channel 62 is pressurized.

  Then, the inside of the discharge channel 62 is pressurized, so that the small diameter meniscus formed in the small diameter nozzle hole 81 is destroyed. When the small-diameter meniscus is destroyed, the ink enters the large-diameter nozzle hole 82 through the lower end opening of the small-diameter nozzle hole 81 (the upper end opening of the large-diameter nozzle hole 82). The ink that has entered the large-diameter nozzle hole 82 spreads wet on the connection surface 76a of the first plate 76. Thereafter, the ink continuously enters the large-diameter nozzle hole 82 to fill the large-diameter nozzle hole 82 with the ink. When the pressure in the discharge channel 62 reaches the large diameter pressure (negative pressure), an appropriate large diameter meniscus is formed in the large diameter nozzle hole 82 by surface tension acting on the inner surface of the large diameter nozzle hole 82. Is done. In the large droplet mode, after an appropriate large-diameter meniscus is formed in the large-diameter nozzle hole 82, the pressure in the discharge channel 62 is changed to a large-diameter pressure due to, for example, a water head difference between the supply sub-tank 8 and the discharge sub-tank 9. To maintain.

  In the large droplet mode, the ink is separated from the large-diameter meniscus by expanding / contracting the volume in the discharge channel 62 by the operation method of the inkjet head 5 described above. As a result, a large droplet having a size corresponding to the large-diameter meniscus falls downward. As a result, large droplets can be discharged through the nozzle holes 71. In the large droplet mode, a driving voltage having an appropriate frequency is applied to the driving electrode so that an appropriate large-diameter meniscus is formed in the large-diameter nozzle hole 82 before and after discharging the large droplet.

  In order to switch from the large droplet mode to the small droplet mode, the pressure in the discharge channel 62 is reduced to a small diameter pressure. That is, the supply pump 35 provided in the ink supply pipe 31 is stopped, and the ink circulation in the ink supply pipe 31 is blocked. At this time, even if the ink flow in the ink supply pipe 31 is interrupted, the ink is continuously discharged from the inkjet head 5 by the action of the suction pump 36.

  Then, the pressure in the discharge channel 62 is reduced, so that the ink filled in the nozzle hole 71 is sucked into the discharge channel 62. That is, the ink filled in the large-diameter nozzle hole 82 is sucked into the small-diameter nozzle hole 81 through the lower end opening of the small-diameter nozzle hole 81, so that the ink is retracted from the large-diameter nozzle hole 82. As shown in FIG. 6, when the pressure in the discharge channel 62 reaches the small diameter pressure, an appropriate small diameter meniscus is formed in the small diameter nozzle hole 81. In the small droplet mode, after an appropriate small-diameter meniscus is formed in the small-diameter nozzle hole 81, the pressure in the discharge channel 62 is maintained at a small-diameter pressure due to a water head difference between the supply sub-tank 8 and the discharge sub-tank 9, for example. .

  Note that the mode switching described above may be performed for the entire printer 1 (all of the inkjet heads 5) or for each inkjet head 5.

As described above, the nozzle plate 51 of the present embodiment is configured to include the small diameter nozzle hole 81 and the large diameter nozzle hole 82 communicating with the small diameter nozzle hole 81 below the small diameter nozzle hole 81.
According to this configuration, a small droplet can be ejected by ejecting ink in a state where a small-diameter meniscus is formed in the small-diameter nozzle hole 81. In this case, in the small droplet mode, the printing range with one droplet can be made smaller than in the large droplet mode. Thereby, for example, by increasing the driving frequency as compared with the large droplet mode, the pitch of the droplets in the Y direction (scanning direction of the inkjet head 5) can be made narrower than that in the large droplet mode, and high resolution printing can be performed. realizable. On the other hand, large droplets can be ejected by ejecting ink while a large-diameter meniscus is formed in the large-diameter nozzle hole 82. In this case, since the printing range with one droplet can be increased as compared with the small droplet mode, high-speed printing can be realized. As described above, since the small droplet mode and the large droplet mode can be switched according to the pressure in the ejection channel 62, the droplet size of the ink ejected from the inkjet head 5 can be easily changed according to the purpose. can do.

In particular, in the present embodiment, since the small diameter nozzle holes 81 and the large diameter nozzle holes 82 are formed to communicate with each other in the Z direction, for example, the small diameter nozzle holes 81 and the large diameter nozzle holes 82 are alternately formed in the X direction. Compared with the case where it exists, the arrangement pitch of the nozzle holes 81 and 82 of the same diameter adjacent in a X direction can be narrowed. Thereby, the pitch of the droplets in the X direction can be narrowed, and the resolution can be improved.
Moreover, since the nozzle holes 81 and 82 of the same diameter are opened on the same plane, the nozzle plate 51 of this embodiment is compared with the case where a plurality of nozzle holes having different inner diameters are opened on the same plane. The optimum meniscus can be easily formed in each of the nozzle holes 81 and 82. Further, since an optimum meniscus can be easily formed in each nozzle hole 81, 82, a difference in inner diameter between the small diameter nozzle hole 81 and the large diameter nozzle hole 82 can be ensured, and a small droplet mode and a large droplet mode can be achieved. It is also possible to increase the difference in droplet size.

In the present embodiment, the connection surface 76a of the first plate 76 has hydrophilicity.
According to this configuration, when overflowing from the small droplet mode to the large droplet mode, the ink overflowing from the small diameter nozzle hole 81 can be wetted and spread into the large diameter nozzle hole 82. Accordingly, it is possible to suppress the ink overflowing from the small diameter nozzle hole 81 from dripping directly through the large diameter nozzle hole 82 (without being wetted and spread on the connection surface 76a or the inner surface of the large diameter nozzle hole 82). As a result, the large diameter nozzle hole 82 can be filled with ink in the large droplet mode.

In the present embodiment, the lower surface of the second plate 77 has water repellency.
According to this configuration, since it is possible to suppress the ink from spreading on the lower surface of the second plate 77, for example, when switching from the small droplet mode to the large droplet mode, the ink leaks from the large diameter nozzle hole 82. Can be suppressed.

In the present embodiment, the nozzle plate 51 is formed by laminating the first plate 76 and the second plate 77.
According to this configuration, the nozzle plate 51 can be formed by stacking the plates 76 and 77 after the small diameter nozzle hole 81 and the large diameter nozzle hole 82 are formed in the plates 76 and 77, respectively. Therefore, the nozzle plate 51 can be easily manufactured compared to the case where the small-diameter nozzle hole 81 and the large-diameter nozzle hole 82 that are continuous in the Z direction are formed on one nozzle plate.

In the present embodiment, the length in the Z direction of the large diameter nozzle hole 82 (second plate 77) is set to be longer than the length in the Z direction of the small diameter nozzle hole 81 (first plate 76).
According to this configuration, the large-diameter meniscus can be accommodated in the large-diameter nozzle hole 82. That is, since the liquid surface of the large-diameter meniscus can be disposed in the large-diameter nozzle hole 82, it is possible to prevent the large-diameter meniscus from being destroyed without being accommodated in the large-diameter nozzle hole 82. Therefore, an appropriate large-diameter meniscus can be stably formed in the large-diameter nozzle hole 82.

  And since the inkjet head 5 and the printer 1 of this embodiment are provided with the nozzle plate 51 mentioned above, the inkjet head 5 and the printer 1 which were excellent in commercial property can be provided.

(Second Embodiment)
Next, a second embodiment will be described. FIG. 8 is a cross-sectional view corresponding to FIG. 4 of the inkjet head 5 according to the second embodiment. This modification is different from the above-described embodiment in that the first plate 76 and the second plate 77 are stacked with the intermediate plate 100 interposed therebetween. In the following description, the same components as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  The nozzle plate 151 shown in FIG. 8 includes the first plate 76 and the second plate 77 described above, and the intermediate plate 100 disposed between the first plate 76 and the second plate 77. The plan view shape of the intermediate plate 100 is the same as that of the first plate 76 and the second plate 77. Further, the thickness of the intermediate plate 100 is equal to or greater than the radius of the lower end opening of the large diameter nozzle hole 82 (that is, the maximum depression amount in the Z direction of the large diameter meniscus). It can be changed as appropriate within the range. Furthermore, for example, a metal material (SUS or the like) is preferably used for the intermediate plate 100. However, the thickness and material of the intermediate plate 100 can be changed as appropriate. For example, the intermediate plate 100 can be formed of a material similar to that of the first plate 76 and the second plate 77 (a resin material (for example, polyimide) or glass in addition to a metal material).

  In the intermediate plate 100, communication holes 101 penetrating the intermediate plate 100 in the Z direction are formed at positions overlapping the small diameter nozzle holes 81 and the large diameter nozzle holes 82 described above when viewed from the Z direction. The communication hole 101 constitutes the nozzle hole 171 of this embodiment together with the small diameter nozzle hole 81 and the large diameter nozzle hole 82. The communication hole 101 is formed to have a uniform inner diameter over the entire Z direction, for example. The inner diameter of the communication hole 101 is larger than the inner diameter of the upper end opening of the large diameter nozzle hole 82. However, the communication hole 101 may be formed in a tapered shape or the like as long as the minimum inner diameter is equal to or larger than the inner diameter of the upper end opening of the large-diameter nozzle hole 82.

According to this configuration, the large-diameter meniscus can be accommodated in the large-diameter nozzle hole 82 (and in the communication hole 101). That is, since the liquid surface of the large-diameter meniscus can be disposed in the large-diameter nozzle hole 82 (and in the communication hole 101), the large-diameter meniscus cannot be accommodated in the large-diameter nozzle hole 82 (and in the communication hole 101). It is possible to suppress the destruction of the large-diameter meniscus. Therefore, an appropriate large-diameter meniscus can be stably formed in the large-diameter nozzle hole 82.
In addition, since the communication hole 101 communicates the lower end opening of the small diameter nozzle hole 81 and the upper end opening of the large diameter nozzle hole 82, the communication hole 101 is also filled with ink in the large droplet mode. In this case, since the inner diameter of the communication hole 101 is larger than the inner diameter of the large-diameter nozzle hole 82, the large-diameter nozzle hole is larger than when ink flows directly from the small-diameter nozzle hole 81 into the large-diameter nozzle hole 82. Ink can be smoothly circulated in 82. That is, since the communication hole 101 functions as a buffer for holding ink between the small diameter nozzle hole 81 and the large diameter nozzle hole 82, insufficient supply of ink into the large diameter nozzle hole 82 occurs in the large droplet mode. Can be suppressed.

  The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the inkjet printer 1 has been described as an example of the liquid ejecting apparatus, but the configuration is not limited thereto. For example, a fax machine or an on-demand printer may be used. The present invention can also be applied to, for example, a large-sized printer that does not have a transport mechanism that transports the recording medium P, a so-called fixed printer that does not have a scanning mechanism that scans the inkjet head 5, and the like.

In the above-described embodiment, the side shoot type inkjet head 5 has been described, but the invention is not limited thereto. For example, the present invention may be applied to a so-called edge shoot type inkjet head that ejects ink from the end of the ejection channel 62 in the extending direction.
In the above-described embodiment, the configuration in which the ejection channels 62 and the non-ejection channels 63 are alternately arranged has been described. However, the configuration is not limited thereto. For example, the present invention may be applied to a so-called three-cycle ink jet head that sequentially ejects ink from all channels.

In the above-described embodiment, the so-called wall-bend type ink-jet head 5 among the piezo-type ink-jet heads 5 has been described. However, the present invention is not limited to this configuration. For example, the present invention is applied to a so-called roof chute type ink jet head (the direction of pressure applied to ink and the direction in which droplets are ejected in the same direction), and other piezoelectric type ink jet heads. It doesn't matter.
Further, the present invention can be applied not only to the piezo type but also to a thermal type inkjet head or the like.

  In the above-described embodiment, the on-carriage printer 1 has been described with the configuration having the main tank 6 and the sub-tanks 8 and 9. However, the configuration is not limited to this configuration, and the configuration without the sub-tanks 8 and 9 (the ink tank is not provided). It may be a configuration mounted on a carriage). Further, a so-called off-carriage type printer 1 in which an ink tank is mounted separately from the carriage 23 may be used.

In the above-described embodiment, the configuration for adjusting the water head difference between the supply sub-tank 8 and the discharge sub-tank 9 by switching the operation of the supply pump 35 and the suction pump 36 has been described, but the configuration is not limited thereto. For example, a moving mechanism that relatively moves the supply sub-tank 8 and the discharge sub-tank 9 in the Z direction may be provided.
Further, the pressure in the discharge channel 62 may be changed by a method other than the water head difference between the supply sub-tank 8 and the discharge sub-tank 9. For example, the supply sub tank 8 may be provided with a pressurized air pump, and the discharge sub tank 9 may be provided with a reduced pressure air pump. In this case, the pressure in the discharge tank 62 can be adjusted by adjusting the pressure in the sub tanks 8 and 9 by the operation of the pressurized air pump or the reduced pressure air pump. In the case where the sub tanks 8 and 9 are not provided, the pressure in the discharge channel 62 can be adjusted by adjusting the pressure in the ink tank provided separately from the carriage 23.

  In the above-described embodiment, the configuration in which the small-diameter nozzle hole 81 and the large-diameter nozzle hole 82 are formed in a tapered shape has been described, but is not limited to this configuration. For example, the inner diameters of the small diameter nozzle hole 81 and the large diameter nozzle hole 82 may be uniform over the entire Z direction.

  In the above-described embodiment, the case where the nozzle plate 51 is formed by stacking the two plates 76 and 77 has been described, but the configuration is not limited thereto. That is, the nozzle plate 51 having the small-diameter nozzle hole 81 and the large-diameter nozzle hole 82 may be integrally formed (one piece). In this case, the nozzle plate can be formed by electroforming or the like. Specifically, first, electroforming is performed on a mold having a small-diameter molding portion corresponding to the small-diameter nozzle hole, thereby forming a primary molded body. Subsequently, after forming a large-diameter molded portion having a shape corresponding to the large-diameter nozzle hole on the mold, electroforming is performed again. As a result, a secondary molded body integrally formed with the primary molded body is formed. Then, by removing the primary molded body and the secondary molded body from the molding die, a nozzle plate in which the primary molded body and the secondary molded body are integrally formed is completed.

  In the above-described embodiment, the configuration in which two nozzle holes having different inner diameters are connected in the Z direction has been described. However, the configuration is not limited to this configuration, and three or more nozzles having a larger diameter toward the downstream side in the ink flow direction. The plurality of nozzle holes may be continuous in the Z direction.

  In addition, in the range which does not deviate from the meaning of this invention, it is possible to replace suitably the component in the embodiment mentioned above by a known component, and you may combine each modification mentioned above suitably.

1 ... Inkjet printer (liquid ejecting device)
5 ... Inkjet head (liquid ejecting head)
51, 151 ... Nozzle plate (injection hole plate, plate body)
76 ... 1st plate 76a ... Connection surface 77 ... 2nd plate 81 ... Small diameter nozzle hole (1st injection hole)
82 ... Large diameter nozzle hole (second injection hole)
100 ... Intermediate plate 101 ... Communication hole

Claims (8)

A plate body having a first injection hole and a second injection hole for injecting liquid;
The second injection hole is formed to have a larger diameter than the first injection hole and communicates with the first injection hole on the downstream side in the liquid flow direction with respect to the first injection hole. Characteristic injection hole plate.   The connection surface which connects the downstream edge of the said flow direction in the said 1st injection hole and the upstream edge of the said flow direction in the said 2nd injection hole among the said plate main bodies has hydrophilic property. The injection hole plate according to claim 1.   3. The injection hole plate according to claim 1, wherein an opening surface of the plate body in which the downstream opening in the flow direction in the second injection hole opens has water repellency. 4. . The plate body is
A first plate in which the first injection holes are formed;
The first plate according to any one of claims 1 to 3, further comprising a second plate that is laminated on the downstream side in the flow direction with respect to the first plate and has the second injection hole formed therein. The injection hole plate according to claim 1. The plate body has an intermediate plate disposed between the first plate and the second plate;
The intermediate plate is formed with a communication hole that communicates the downstream opening in the flow direction in the first injection hole and the upstream opening in the flow direction in the second injection hole,
The injection hole plate according to claim 4, wherein an inner diameter of the communication hole is formed to be equal to or larger than an inner diameter of the second injection hole.   The injection hole according to any one of claims 1 to 5, wherein a length of the second injection hole in the flow direction is longer than a length of the first injection hole in the flow direction. plate. The injection hole plate according to any one of claims 1 to 6,
And an actuator plate having a channel that is disposed upstream of the injection hole plate in the flow direction and communicates with the second injection hole through the first injection hole. head.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 7.

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